acert: Implement a plugin finding, validating and evaluating attribute certs

This validator checks for any attribute certificate it can find for validated
end entity certificates and tries to extract group membership information
used for connection authorization rules.

configure.ac

@@ -165,6 +165,7 @@ ARG_ENABL_SET([mysql],          [enable MySQL database support. Requires libmysq
 ARG_ENABL_SET([sqlite],         [enable SQLite database support. Requires libsqlite3.])
 # authentication/credential plugins
 ARG_ENABL_SET([addrblock],      [enables RFC 3779 address block constraint support.])
+ARG_ENABL_SET([acert],          [enable X509 attribute certificate checking plugin.])
 ARG_ENABL_SET([agent],          [enables the ssh-agent signing plugin.])
 ARG_DISBL_SET([constraints],    [disable advanced X509 constraint checking plugin.])
 ARG_ENABL_SET([coupling],       [enable IKEv2 plugin to couple peer certificates permanently to authentication.])
@@ -1090,6 +1091,7 @@ ADD_PLUGIN([nonce],                [s charon nm cmd])
 ADD_PLUGIN([x509],                 [s charon openac scepclient pki scripts attest nm cmd])
 ADD_PLUGIN([revocation],           [s charon nm cmd])
 ADD_PLUGIN([constraints],          [s charon nm cmd])
+ADD_PLUGIN([acert],                [s charon])
 ADD_PLUGIN([pubkey],               [s charon cmd])
 ADD_PLUGIN([pkcs1],                [s charon openac scepclient pki scripts manager medsrv attest nm cmd])
 ADD_PLUGIN([pkcs7],                [s charon scepclient pki scripts nm cmd])
@@ -1229,6 +1231,7 @@ AM_CONDITIONAL(USE_NONCE, test x$nonce = xtrue)
 AM_CONDITIONAL(USE_X509, test x$x509 = xtrue)
 AM_CONDITIONAL(USE_REVOCATION, test x$revocation = xtrue)
 AM_CONDITIONAL(USE_CONSTRAINTS, test x$constraints = xtrue)
+AM_CONDITIONAL(USE_ACERT, test x$acert = xtrue)
 AM_CONDITIONAL(USE_PUBKEY, test x$pubkey = xtrue)
 AM_CONDITIONAL(USE_PKCS1, test x$pkcs1 = xtrue)
 AM_CONDITIONAL(USE_PKCS7, test x$pkcs7 = xtrue)
@@ -1454,6 +1457,7 @@ AC_CONFIG_FILES([
 	src/libstrongswan/plugins/x509/Makefile
 	src/libstrongswan/plugins/revocation/Makefile
 	src/libstrongswan/plugins/constraints/Makefile
+	src/libstrongswan/plugins/acert/Makefile
 	src/libstrongswan/plugins/pubkey/Makefile
 	src/libstrongswan/plugins/pkcs1/Makefile
 	src/libstrongswan/plugins/pkcs7/Makefile